[removed] vs script defer

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爱一瞬间的悲伤
爱一瞬间的悲伤 2021-02-07 15:45

Here it\'s said, that there are 4 readyState possible values for html documents:

uninitialized - Has not started loading yet
loading

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  • 2021-02-07 16:18

    Read on to http://www.w3.org/html/wg/drafts/html/master/scripting-1.html#attr-script-defer:

    There are three possible modes that can be selected using these attributes. If the async attribute is present, then the script will be executed asynchronously, as soon as it is available. If the async attribute is not present but the defer attribute is present, then the script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page.

    http://www.w3.org/TR/html5/syntax.html#the-end tells you that deferred scripts run first:


    Execute the first script in the list of scripts that will execute when the document has finished parsing.

    Then the DOMContentLoaded event:

    Queue a task to fire a simple event that bubbles named DOMContentLoaded at the Document.

    load events fire after both of these, always.

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